We will pursue three somewhat related directions concerned with the molecular interactions of DNA in chromosomes: 1) We will investigate the nature of the long-range order in polymer-condensed DNA where optical microscopy has shown that the DNA packing resembles that found in certain compact chromosomes. The experiments will be based on freeze-fracture-etch observations on the condensed DNA particles following the techniques we have recently developed for examining single crystals of DNA. 2) We will examine the effect of proteins and intercalating agents on the polymer-induced condensation. Our hypotheses as to the physical basis of condensation suggest a distinct regulatory role for DNA binding proteins. 3) We will initiate studies on the characterization of specific, restriction enzyme fragments of eukaryotic DNA with respect to their role in the chromosome. This work will rely on estabished techniques of fragmentation and characterization, and also on the development of transport methods which depend on different molecular parameters.